The helmet on post 1227 is from WW 1 or WW 2 ? One friend found one like your on Isonzo front , the helmet was in experimental use in Austrohungarian army.
In the german army WW 1 could be used by telegrafist.
Was on your,s dig place also WW1 battles?

Confirm:it is a German WWI Helmet M18, to later used finnish troops from 1918-1945,Russian White Guard in North Russia 1918-1921 (fighting between General Yudenich and bolshewiks troops).Helmet type "Radiotechnic"
Digplace near Petrozavodsk-capital of Karelia